Annular baffle

ABSTRACT

A baffle assembly for an etching apparatus is disclosed. The baffle assembly comprises a ring and a lower baffle portion having a curved wall extending between a flange portion and a lower frame portion. A heating assembly may be present within the lower frame portion to control the temperature of the baffle. The baffle assembly may help confine the plasma within the processing space in the chamber. The ring may comprise silicon carbide and the lower baffle portion may comprise aluminum.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. provisional patent applicationSer. No. 60/914,583, filed Apr. 27, 2007, which is herein incorporatedby reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention generally relate to a baffleassembly for confining a plasma in an etching chamber.

2. Description of the Related Art

Plasma processing of semiconductor substrates in the manufacture ofmicroelectronic integrated circuits is used in dielectric etching, metaletching, chemical vapor deposition (CVD) and other processes. Insemiconductor substrate processing, the trend towards increasinglysmaller feature sizes and line-widths has placed a premium on theability to mask, etch, and deposit material on a semiconductorsubstrate, with greater precision.

Etching may be accomplished by applying radio frequency (RF) power to aworking gas supplied to a processing region over a substrate supportedby a support member. The resulting electric field creates a reactionzone in the processing region that excites the working gas into aplasma. The support member may be biased to attract ions within theplasma towards the substrate supported thereon. Ions migrate towards aboundary layer of the plasma adjacent to the substrate and accelerateupon leaving the boundary layer. The accelerated ions produce the energyrequired to remove, or etch, the material from the surface of thesubstrate. As the accelerated ions can etch other components within theprocessing chamber, confining the plasma to the processing region abovethe substrate may be beneficial.

Unconfined plasmas may cause etch-byproduct (typically polymer)deposition on the chamber walls and could also etch the chamber walls.Etch-byproduct deposition on the chamber walls could cause the processto drift. The etched materials from the chamber walls could contaminatethe substrate by re-deposition and/or could create particles for thechamber. In addition, unconfined plasmas could also cause etch-byproductdeposition in the downstream areas. The accumulated etch-byproduct mayflake off and result in particles.

Therefore, there is a need in the art for an improved baffle assemblyfor confining plasma within a processing region inside the plasmachamber.

SUMMARY OF THE INVENTION

A baffle assembly for an etching apparatus is disclosed. The baffleassembly includes a ring and a lower baffle portion having a curved wallextending between a flange portion and a lower frame portion. A heatingassembly may be present within the lower frame portion to control thetemperature of the baffle. The baffle assembly may help confine theplasma within the processing space in the chamber. The ring may comprisesilicon carbide and the lower baffle portion may comprise aluminum.

In one embodiment, baffle assembly is disclosed. The baffle assembly mayinclude a ring and a base portion coupled to the ring. The base portioncomprises a flange having a first diameter, a lower frame portion havinga second diameter less than the first diameter, and a first wall coupledbetween the flange and the lower frame portion. The first wall curvesout from the lower frame portion to the flange.

In another embodiment, a ring for use in a baffle assembly of an etchingchamber is disclosed. The ring may include a top wall extending to afirst diameter, an outer wall having a second diameter greater than thefirst diameter, and a second wall coupled between the top wall and theouter wall. The second wall curves from the top wall at the firstdiameter to the outer wall at the second diameter.

In another embodiment, a base portion of a baffle is disclosed. The baseportion may include a flange having a first diameter, a lower frameportion having a second diameter less than the first diameter, and afirst wall coupled between the flange and the lower frame portion. Thefirst wall curves out from the lower frame portion to the flange.

In another embodiment, a baffle assembly is disclosed. The baffleassembly may include a ring and a base portion coupled to the ring. Thebase portion comprises a flange having a first diameter, a lower frameportion having a second diameter less than the first diameter, asupporting portion for supporting the flange, and a heating assembly.

In another embodiment, a base portion of a baffle is disclosed. The baseportion may include a flange having a first diameter, a lower frameportion having a second diameter less than the first diameter, asupporting portion for supporting the flange, and a heating assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 is a schematic view of a plasma processing chamber according toone embodiment of the invention.

FIG. 2A is a cross sectional view of a baffle assembly according to oneembodiment of the invention.

FIG. 2B is a cross sectional view of cut out A from FIG. 2A.

FIG. 2C is a cross sectional view of cut out B from FIG. 2B.

FIG. 3A is a top view of a ring according to one embodiment of theinvention.

FIG. 3B is a cross sectional view of a ring of FIG. 3A.

FIGS. 4A and 4B are schematic perspective views of a lower baffleportion according to one embodiment of the invention.

FIG. 4C is a cross sectional view of cut out C from FIG. 4A.

FIG. 4D is a cross sectional view of FIG. 4C.

FIG. 5 shows a baffle assembly according to another embodiment of theinvention.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements disclosed in oneembodiment may be beneficially utilized on other embodiments withoutspecific recitation.

DETAILED DESCRIPTION

The present invention comprises a baffle assembly for confining a plasmato a processing region in a plasma processing apparatus. While theinvention will be described below in relation to an ENABLER® etchingsystem available from Applied Materials, Inc., Santa Clara, Calif., itis to be understood that the invention may be used in other processingchambers including physical vapor deposition (PVD) chambers, CVDchambers, etc., including those chambers sold by other manufacturers.

FIG. 1 illustrates an example of a plasma reactor, such as the ENABLER®etching system manufactured by Applied Materials, Inc., of Santa Clara,Calif., that includes a reactor chamber 100, which may include liners toprotect the walls, with a substrate support (or pedestal) 105 at thebottom of the chamber 100 supporting a semiconductor substrate. Thechamber 100 is bounded at the top by a disc shaped overhead aluminumelectrode 125 supported at a predetermined gap length above thesubstrate on grounded chamber body 127 by a dielectric (quartz) seal130. A power generator 150 applies very high frequency (VHF) power tothe electrode 125. VHF is typically between about 30 MHz to about 300MHz and is one of the RF bands, which range from about 10 kHz to about10 GHz. In one embodiment, the VHF source power frequency is 162 MHz fora 300 mm substrate diameter. VHF power from the generator 150 is coupledthrough a coaxial cable 162 matched to the generator 150 and into acoaxial stub 135 connected to the electrode 125. The stub 135 has acharacteristic impedance, resonance frequency, and provides an impedancematch between the electrode 125 and coaxial cable 162 or the VHF powergenerator 150. The chamber body is connected to the VHF return (VHFground) of the VHF generator 150. Bias power is applied to the substrateby a bias power RF signal generator 102 coupled through a conventionalimpedance match circuit 104 to the substrate support 105. The powerlevel of the bias generator 102 controls the ion energy near thesubstrate surface. The bias power (typically at 13.56 MHz) is typicallyused to control ion energy, while the VHF source power is applied to theoverhead electrode to govern plasma density. A vacuum pump system 111evacuates the chamber 100 through a plenum 112.

The substrate support 105 includes a metal pedestal layer 106 supportinga lower insulation layer 107, an electrically conductive mesh layer 108overlying the lower insulation layer 107 and a thin top insulation layer110 covering the conductive mesh layer 108. The semiconductor workpieceor substrate is placed on top of the top insulation layer 110. Thesubstrate support 105 and the substrate form a cathode during substrateprocessing. If the substrate is not present, the substrate support 105is the cathode during plasma processing. The electrically conductivemesh layer 108 and the metal pedestal layer 106 may be formed ofmaterials such as molybdenum and aluminum respectively. The insulationlayers 107 and 110 may be formed of materials such as aluminum nitrideor alumina. The conductive mesh layer 108 supplies the RF bias voltageto control ion bombardment energy at the surface of the substrate. Theconductive mesh 108 also can be used for electrostatically chucking andde-chucking the substrate, and in such a case can be connected to achucking voltage source in the well-known fashion. The conductive mesh108 therefore is not necessarily grounded and can have, alternately, afloating electric potential or a fixed D.C. potential in accordance withconventional chucking and de-chucking operations. The substrate support105, in particular the metal pedestal layer 106, typically (but notnecessarily) is connected to ground, and forms part of a return path forVHF power radiated by the overhead electrode 125.

In order to improve the uniformity of impedance across the substratesupport, a dielectric cylindrical sleeve 113 is designed to surround theRF conductor 114. The axial length and the dielectric constant of thematerial constituting the sleeve 113 determine the feed point impedancepresented by the RF conductor 114 to the VHF power. By adjusting theaxial length and the dielectric constant of the material constitutingthe sleeve 113, a more uniform radial distribution of impedance can beattained, for more uniform capacitive coupling of VHF source power.

A terminating conductor 165 at the far end 135 a of the stub 135 shortsthe inner and outer conductors 140, 145 together, so that the stub 135is shorted at its far end 135 a. At the near end 135 b (the unshortedend) of the stub 135, the outer conductor 145 is connected to thechamber body via an annular conductive housing or support 175, while theinner conductor 140 is connected to the center of electrode 125 via aconductive cylinder 176. A dielectric ring 180 is held between andseparates the conductive cylinder 176 and the electrode 125.

The inner conductor 140 can provide a conduit for utilities such asprocess gases and coolant. The principal advantage of this feature isthat, unlike typical plasma reactors, the gas line 170 and the coolantline 173 do not cross large electrical potential differences. Theytherefore may be constructed of metal, a less expensive and morereliable material for such a purpose. The metallic gas line 170 feedsgas inlets 172 in or adjacent the overhead electrode 125 while themetallic coolant line 173 feeds coolant passages or jackets 174 withinthe overhead electrode 125.

Since plasma density is relatively low near the wall, a baffle assembly131 placed around the substrate with a distance (or gap) from the innerchamber wall 128 may confine the plasma. The distance (or gap) betweenthe edge of the baffle assembly 131 and the inner chamber wall 128cannot be too large. If the gap distance is larger than the plasmasheath thickness near the chamber wall, it could increase the amount ofplasma being drawn away from the reaction zone above the substrate andtoward the chamber wall and downstream, which makes the plasma lessconfined. The distance (or gap) between the edge of the baffle assembly131 and the inner chamber wall 128 cannot be too small either, since theflow resistance, which affects the chamber pressure, would increase toan unacceptable level. Therefore, the baffle assembly 131 is placedaround the substrate with a suitable distance from the inner chamberwall 128 to provide good plasma confinement and low flow resistance.

FIG. 2A is a cross sectional view of a baffle assembly 200 according toone embodiment of the invention. The baffle assembly 200 comprises aring 202 and a base portion 204. The base portion 204 also comprises aflange 206 having a first diameter “D” of between about 19 inches andabout 20 inches. A curved wall 208 extends from the flange 206 to aheating assembly 214 that is coupled with the base portion 204. Thecurved wall 208 provides support for the flange 206 extending from thebase portion 204 as well as the ring 202. The innermost outer wall 220of the base portion 204 has a diameter “G” of between about 14 inchesand about 16 inches. A notch 222 may also be present on the bottom ofthe base portion 204. A heating assembly may be present in the baffleassembly 200. The heating assembly 214 may comprise a heating tube 228brazed inside the base portion 204.

FIG. 2B is a cross sectional view of cut out A from FIG. 2A. A ledge 210may be disposed radially inward of the flange 206. A curved wall 218 mayextend between the outer wall 218 of the flange 206 and a bottom wall216 of the flange 206.

FIG. 2C is a cross sectional view of cut out B from FIG. 2B. The ring202 may be bonded to the base portion 204 with one or more spacers 212disposed therebetween. One or more O-rings 224 may also be disposedbetween the base portion 204 and the ring 202 to provide a bonded sealbetween the ring 202 and the base portion 204. The O-rings 224 may bedisposed within a notch formed in the base portion 204.

FIG. 3A is a top view of a ring 300 according to one embodiment of theinvention. FIG. 3B is a cross sectional view of the ring 300 of FIG. 3A.The ring 300 may comprise a top wall 302 having a diameter “E” betweenabout 18 inches and about 19 inches. The ring 300 may also comprise anouter wall 308 having a diameter “F” between about 19 inches and about20 inches. A curved wall 304 may extend between the outer wall 308 andthe top wall 302. The ring 300 may comprise an opening 306 having adiameter “I” between about 13 inches and about 14 inches. In oneembodiment, the diameter of the outer wall 308 of the ring may besubstantially equal to the diameter of the flange 206.

FIGS. 4A and 4B are schematic perspective views of a lower baffleportion according to one embodiment of the invention. FIG. 4A is aschematic perspective view of the lower baffle portion viewed from thebottom. FIG. 4B is a schematic view of the lower baffle portion viewedfrom the top. As may be seen in FIG. 4A, the bottom of the lower baffleportion has a female receptacle for providing power to the heatingassembly. FIG. 4C is a cross sectional view of cut out C from FIG. 4Ashowing the female receptacle 400. As may be seen from FIG. 4C, thereceptacle comprises three slots 402 for receiving a power plug.

FIG. 4D is a cross sectional view of FIG. 4C. FIG. 4D shows a crosssectional view of the female receptacle 400 shown in FIG. 4C. The lowerbaffle portion comprises a top portion 404 coupled with a bottom portion406. Fastening mechanisms 408 may be used to secure the femalereceptacle to the bottom portion 406. In one embodiment, the fasteningmechanism 408 is a screw, but it is to be understood that otherfastening mechanisms 408 may be utilized. Two electrical contacts 412are disposed in the receptacle 410 to deliver the electrical power tothe heating tubes 414 that are brazed within the lower baffle portion.

FIG. 5 shows a baffle assembly 500 according to another embodiment ofthe invention. As may be seen in FIG. 5, the baffle assembly 500comprises a ring 502 coupled with a lower portion 504 having a flange506 supported by a support structure 508. In one embodiment, the supportstructure 508 may comprise a step or corner shape. While a step orcorner shape is shown as the support structure 508, it is to beunderstood that other shapes may be utilized to provide mechanicalstrength to support the flange 506, including curved walls as discussedabove.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

The invention claimed is:
 1. A baffle assembly, comprising: a ring; abase portion comprising: a flange having a first diameter, the flangecoupled to the ring, wherein the first diameter of the flange is betweenabout 19 inches to about 20 inches and wherein the first diameter of theflange is aligned with an outside diameter of the ring; a lower frameportion having a second diameter less than the first diameter; and afirst concave wall coupled between the flange and the lower frameportion, wherein the first wall curves out from the lower frame portionto the flange; and a heating assembly directly coupled to the lowerframe portion on a side of the base portion opposite the ring, the baseportion and heating assembly being concentrically stacked.
 2. The baffleassembly of claim 1, wherein the ring comprises silicon and wherein thebase portion comprises aluminum.
 3. The baffle assembly of claim 1,wherein the base portion further comprises a ledge disposed radiallyinward from the first wall.
 4. The baffle assembly of claim 1, furthercomprising: one or more spacers coupled between the ring and the baseportion.
 5. The baffle assembly of claim 1, wherein the ring furthercomprises: a top wall extending to a third diameter; an outer wallhaving a fourth diameter greater than the third diameter; and a secondwall coupled between the top wall and the outer wall, wherein the secondwall curves from the top wall at the third diameter to the outer wall atthe fourth diameter, wherein the fourth diameter is substantially equalto the first diameter.
 6. The baffle assembly of claim 1, wherein thebase portion further comprises: a bottom wall having a third diametergreater than the second diameter, but less than the first diameter; anda second wall curving between the third diameter and the first diameter.7. The baffle assembly of claim 1, wherein the ring comprises an insidediameter of between about 13 inches to about 14 inches.
 8. The baffleassembly of claim 1, wherein the heating assembly further comprises areceptacle for providing power to the heating assembly.
 9. The baffleassembly of claim 1, wherein the heating assembly further comprises abrazed heating tube.
 10. A baffle assembly, comprising: a ring; a baseportion comprising: a flange having a first diameter, the flange coupledto the ring; a lower frame portion having a second diameter less thanthe first diameter; and a first concave wall coupled between the flangeand the lower frame portion, wherein the first wall curves out from thelower frame portion to the flange; a stepped portion comprising a ledgehaving an outside diameter of between about 13 inches to about 14inches, wherein the outside diameter of the ledge is aligned with aninside diameter of the ring; and a heating assembly directly coupled tothe lower frame portion on a side of the base portion opposite the ring,the base portion and heating assembly being concentrically stacked.